Granulated fatty alcohol sulfate products

ABSTRACT

A granulated fatty alcohol sulphate is characterized by a bulk density greater than 600 g/lit when no consolidation stress is imparted, it has a particle size-distribution such that at least 15% of the particles are larger than 1000 μm, and less than 10% of the particles are smaller than 250 μm, and has a bulk density which is dependent on the consolidation stress in the range 200 kg/cm 2  to at least 750 kg/cm 2 .

FIELD OF THE INVENTION

The present invention relates to novel free-flowing concentrated fattyalcohol sulphates in granular form and to a process for theirproduction.

BACKGROUND OF THE INVENTION

Fatty alcohol sulphates (FAS) are surfactants used for variousapplications, such as in synthetic soaps, toothpastes, cosmetics andother personal care products, emulsifying agents in polymerizationprocesses, and household and industrial cleaning formulations. Theprocess for the manufacturing of concentrated fatty alcohol sulphateswhich is known in the art consists of three consecutive steps,namely: 1) sulphation of the organic raw material, which is an alcoholof natural or synthetic source having a chain length of C₈ to C₂₀, bySO₃ ; 2) neutralization of the unstable acidic alcohol sulphate producedto form stable salt of the cation used (e.g., sodium, potassium,ammonium, magnesium, or mono-, di- or triethanol amines); and 3) drying.The neutralized product can be processed as a dilute liquid with 25-35%active material, or as a concentrated semi-solid with 60-75% activematerial, where the active agent may be, for example, sodium alcoholsulphate. The final stage of the process is the drying of theneutralized salts of FAS, to obtain the non-sticky solid form.

THE PRIOR ART

The prior art products present several drawbacks: they are friable, verydusty, and prone to serious processing problems associated with lowdensity. Certain ecological problems have also been noted, as the resultof the small particles carry-over.

In order to overcome the known problems, manufacturers had to introducea subsequent stage of compacting or kneading the dry solids into needlesof various dimensions. Thus, the dustiness and irritation of thematerial is somewhat reduced. However, this stage also substantiallyaffects the rate of water dissolution of the product.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved product, whichovercomes the drawback of prior art granular fatty alcohol sulphates.

It is another object of the invention to provide a process for themanufacturing of such improved granular products, which is simple,inexpensive and industrially applicable.

Other objectives of the invention will become apparent as thedescription proceeds.

In order to overcome the problems of the known art detailed above, theinvention provides a novel product of improved properties. The productof the invention is obtained through a manufacturing method involvingtwo first stages, namely the sulphation and neutralization, which arecarried out in a conventional way. The third stage, which is the dryingprocess of the invention, as described below, leads to a final productwhich is physically different from presently available products.

The granulated fatty alcohol sulphate of the invention is characterizedin that:

It has a bulk density greater than 600 g/lit when no consolidationstress is imparted;

It has a particle size-distribution such that at least 15% of theparticles are larger than 1000 μm, and less than 10% of the particlesare smaller than 250 μm; and

It has a bulk density which is dependent on the consolidation stress inthe range 200 kg/cm² to at least 750 kg/cm².

"Consolidation stress" is meant to indicate the stress which is a resultof a pressure gradient developed on the particle during flow.

According to a preferred embodiment of the invention, the granulatedfatty alcohol sulphate of the invention has:

a bulk density of about 700 g/lit;

a particle size-distribution such that about 17% of the material islarger than 1000 μm, and less than 8% of the material is smaller than250 μm.

Unless otherwise indicated, all percentages given herein are by weight.The product according to the invention contains sodium orsodium/potassium salts of lauryl alcohol sulphate, having the structuralformula of ROSO₃ M wherein R is C₁₀ -C₂₂ alkyl and M may be selectedfrom among Na, K, Mg, Na/K, ammonium, mono-, di- or triethanol amines.The alkyl range used as well as the Na/K ratio and the molecular weightof the resulting product may be varied according to the end productrequirements. Illustrative examples of such alkyls are Lorol C₁₀ -C₂₂,Lorol C₁₂, Lorol Spezial (C₁₂ -C₁₄), Lorol V (C₁₂ -C₁₆), Lorol C₁₂ -C₁₈,Stenol 1822A (C₁₈ -C₂₂)(all of these ex. Henkel), and the like.

The granulated fatty alcohol sulphate according to the invention, asstated above, exhibits excellent dissolution properties in water.Furthermore, the granular product obtained according to the invention isfree-flowing, and is very convenient to use as a raw material in furtherprocessing.

Illustrative examples of product density, as measured for severalsamples having various percentages of dry matter are:

    ______________________________________                                        Bulk Density (gr/cc)                                                                           % Dry Matter                                                 ______________________________________                                        0.60             95.8                                                         0.72             99.4                                                         0.80             99.4                                                         0.86             97.0                                                         0.88             99.5                                                         ______________________________________                                    

All the above and other characteristics and advantages of the inventionwill be better understood through the following illustrative andnon-limitative description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows the rate of drying obtained in Examples 1 and 2, whereinline A represents the drying rate of LAS NP (Example 1) and line Brepresents the drying rate of LAS NP+IPA (Example 2).

FIG. 2 shows the drying and granulating equipment used in theexperiments of Examples 1 and 2.

FIG. 3 shows SEM micrographs of particles obtained in Example 1, usingX15 magnification.

FIG. 4 shows SEM micrographs of particles obtained in Example 1, usingX55 magnification.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The improved granulated fatty alcohol sulphates of the invention areobtained by slowly drying under vacuum a material consisting essentiallyof fatty alcohol sulphate, having a total dry matter content between 62wt % and 80 wt %, while solid mixing means are provided to mechanicallymix the drying mixture during the drying process. The remaining 38-20 wtof dry matter typically consists of a solvent or a mixture of solvents,unsulphated fatty alcohol (0.5-2.0 wt %), NaCl (0-0.5 wt %) and Na₂ SO₄(1.0 wt %).

According to a preferred embodiment of the invention the solventconsists essentially of water. According to another preferred embodimentof the invention, the solvent is a mixture of water and an organicsolvent. Suitable organic solvents that can be used are, e.g., ethanol,propanol, isopropanol, acetone, methyl ethyl ketone, polyethylene glycolor the like.

According to another preferred embodiment of the invention, additivesand components like co-surfactants or builders may be added to theproduct. Suitable co-surfactants that can be used are anionicsurfactants, e.g., dodecyl benzene sulphonate and toluene sulphonate,nonionic surfactants, e.g., ethoxylated fatty alcohols, and cationicsurfactants, e.g., quaternary amido compounds, and the like.

As will be appreciated by the skilled person, the advantages of theinvention are achieved by the combined effect of a slow drying, such ascan be achieved by vacuum drying in rotary equipment, and mechanicalmixing of the slurry/solid material during drying, which results in thegranulation being effected during drying. In one preferred embodiment ofthe invention the vacuum is maintained at a level comprised between 5and 60 mbar, absolute pressure. Other vacuum levels can of course beused, but they may be needlessly deep, or may require too long dryingtimes to be operated with high economic advantage and, therefore, arenot preferred, but they of course are within the ambit of the invention.

According to a specific preferred embodiment of the invention theprocess is carried out in a mixing chamber coupled to vacuum generatingmeans. In one embodiment of the invention the mixing means comprisescraper blades moving near the walls of the mixing chamber.Preferably--but not limitatively--the distance between the scraperblades and the wall is between 0.1 and 10 mm, and the scraper bladesrotate at a speed between 10 and 150 rpm.

The actual heating method is not essential to the invention, and anysuitable heating method and apparatus can be employed. One convenientheating method, however, is that in which heat is supplied to thematerial to be dried by a heating jacket provided around the dryingchamber.

As will be apparent to the skilled person, the invention is not limitedto any specific fatty alcohol sulphate. Preferred fatty alcohols are theC₁₀ -C₂₂ alcohols, e.g. sodium lauryl sulphate.

EXAMPLE 1

The arrangement shown in FIG. 2 was used in this experiment. The productis transferred from a supply tank 1, by using a pump 2, to a mixerdryer, 4. The heat required in the process is supplied by the heatingmedium 3, introduced into the dryer. The whole process is carried outunder sub-atmospheric pressure, which is maintained by the vacuum system5.

A 300 liter horizontal, jacketed drying chamber with rotary mixingblades was filled with 60 kg of Zoharpon LAS 70, containing sodium saltof lauryl alcohol sulphate. The structural formula of Zoharpon LAS 70 isROSO₃ M, wherein R is alkyl C₁₂ -C₁₆ and M is Na. Stem was applied inthe jacket and vacuuming was gradually increased until the moisturecontent of the product reached 1%. The actual rate of drying is shown inFIG. 1, in which the amount of water drawn from the sample is given as afunction of time (line A).

The resulting material was characterized as follows:

bulk density: 720 g/lit.

water dissolution time of 2.05 min. at 20° C.

particle size distribution: as shown in Table I below.

two peaks in the X-ray analysis (CuKα, 40KV, 18mA), in the angle

range 5°<2θ<8°, one at about 6.5° and the second at about 7.8°.

the particles obtained had a spherical form, as may be seen in FIGS. 3and 4.

As may be seen from FIGS. 3 and 4, the product obtained has apolycrystalline structure composed essentially of round particles havinga smooth surface.

The product was compared with a commercially available product (TexaponZHK, ex Henkel), which is a sodium lauryl sulphate having a density of0.21-0.28 gr/cc, and which comprises a C₁₂ -C₁₈ alkyl, and thecorresponding results are reported in Table I below:

                  TABLE I                                                         ______________________________________                                        Size (μm)                                                                              Zoharpon LAS NP                                                                             Texapon ZHK                                         ______________________________________                                        >1000       17.28%        0.1%                                                 850-1000   15.46%        0.19%                                               710-850     10.66%        0.3%                                                600-710     11.8%         0.49%                                               500-600     11.4%         3.14%                                               300-500     24.5%         26.99%                                              250-300     1.1%          19.53%                                              150-250     5.6%          25.61%                                               45-150     2.1%          23.45%                                              <45         0.1%          0.2%                                                TOTAL:      100.00%       100.00%                                             ______________________________________                                    

EXAMPLE 2

Example 1 was repeated, but 20 liters of isopropyl alcohol were added to60 kg of Zoharpon LAS 70, before drying, and the two materials weremixed. The drying rate of the solution in said chamber is given in FIG.1 (line B), as in the previous example.

EXAMPLE 3 Rate of Dissolution in Water

The following experiment was carried out to compare the rate ofdissolution of a product according to the invention with thecommercially available product Texapon ZHK (ex Henkel). The conditionsand results were as follows: 3 Wt % of the tested material were added towater at 20° C. and were stirred using a magnetic stirrer. The materialsused were as in Example 2, and the time required to reach a clearsolution was measured. Results were as follows:

    ______________________________________                                                       Dissolution time                                                                          Dissolution rate                                   Material       [min]       [gr/gr water · min]                       ______________________________________                                        ZOHARPON LAS NP                                                                              2.05        0.015                                              TEXAPON K12    5.0         0.006                                              (GRANULAR)                                                                    ______________________________________                                    

EXAMPLE 4

The following experiment was carried out to compare the built density ofa product according to the invention with the commercially availableproduct Texapon ZHK (ex Henkel).

The samples were compared under three stress ranges: no stress, lowstress and high stress. The results obtained for the bulk density ing/lit are given in Table II.

                  TABLE II                                                        ______________________________________                                        stress applied                                                                            Bulk Density (g/lit)                                              [kg/cm]     Zoharpon LAS NP                                                                             Texapon ZHK                                         ______________________________________                                        no stress   696           294                                                 0.077       727           319                                                 0.4         739           347                                                 200         1320          1186                                                999         1367          1186                                                ______________________________________                                    

EXAMPLE 5

In order to compare the flowability of a product according to theinvention with Texapon ZHK, the following shear test was conducted.

The test was carried out using a bulk of particles introduced into ashear tester. The shear tester was used for the measurement of the angleof the wall friction (Φ'). The procedure used to measure the horizontalforces required sliding a sample of bulk solid under a given normal loadacross a piece of material. ##EQU1##

Knowing tan Φ', it is possible to assess whether or not mass flow ispossible in a particular set up. The consolidation force applied was inthe range 0.43 kg. to 20 kg. The actual force required for the shear wasmeasured and subsequently used for calculating the consolidationstresses, as well as angle of internal friction, unconfined yieldstrength and major consolidation stress.

The first set of tests was carded out when the consolidation time wasequal to zero. The second test was done after 24 hours of consolidationunder consolidation forces of 0.84 kg. to 14 kg.

From the results of these tests, the flow function, FF, has beencalculated. The flow function is defined as the ratio of majorconsolidation stress (W_(m)) to the unconfined yield strength (W_(c)).Wherein, "unconfined yield strength" is meant to indicate the majorconsolidation stress when the shear stress is equal to zero. The flowfunction is used to characterize

    ______________________________________                                        FF < 2          non-flowable solids (sticky)                                  2 < FF < 4      cohesive (flowable)                                           4 < FF < 10     easy flowing                                                  FF > 10         free flowing                                                  ______________________________________                                    

The results obtained are presented in Table III.

                  TABLE III                                                       ______________________________________                                                          FLOW                                                                          FUNCTION FF                                                 Consolidation                                                                            Consolidation                                                                              Zoharpon  Texapon                                     force [kg] time [hr.]   LAS NP    ZHK                                         ______________________________________                                        0.84        0           5.17      5.81                                                   24           0.56      0.46                                        2.8         0           5.18      6.11                                                   24           0.93      0.76                                        7.0         0           5.84      6.44                                                   24           1.48      1.26                                        14.0        0           8.32      8.18                                                   24           2.48      1.88                                        internal sheer angle                                                                              25.5      37.2                                            ______________________________________                                    

The above descriptions and examples have been given for the purpose ofillustration, and are not intended to limit the invention in any way.Many modifications can be effected in the various starting materials,additives and process conditions, all without exceeding the scope of theinvention.

We claim:
 1. A granulated fatty alcohol sulphate, characterized inthat:It has a bulk density greater than 600 g/lit when no consolidationstress is imparted; It has a particle size-distribution such that atleast 15% of the particles are larger than 1000 μm, and less than 10% ofparticles are smaller than 250 μm; and It has a bulk density which isdependent on the consolidation stress in the range 200 kg/cm² to atleast 750 kg/cm².
 2. A granulated fatty alcohol sulphate according toclaim 1, having an internal shear angle of no more than 30°.
 3. Agranulated fatty alcohol sulphate according to claim 1, of the chemicalformula of ROSO₃ M, wherein R is C₁₀ -C₂₂ alkyl and M is selected fromamong Na, K, Na/K, Mg, ammonium, mono-, di- or triethanol amines.
 4. Agranulated fatty alcohol sulphate according to claim 1, characterizedby:a bulk density of about 700 g/lit; and a particle size-distributionsuch that about 17% of particles is larger than 1000 μm, and less than8% is smaller than 250 μm.
 5. A granulated fatty alcohol sulphateaccording to claim 1, having two peaks in the X-ray spectrum (CuKα, 40KV, 18 mA), in the angle range 5°<20<8°.
 6. A granulated fatty alcoholsulphate of claim 5, wherein the first peak is at about 6.5° and thesecond at about 7.8°.
 7. A granulated fatty alcohol sulphate accordingto claim 1, having a dissolution rate of 0.015 gr/gr water.min at 20° C.